Earthworking vehicle

ABSTRACT

A shovel loader having a boom, a bucket pivoted thereto, and a quadrilateral linkage interconnecting the bucket and the loader has apparatus for automatically positioning the bucket in the desired digging position. The bucket control valve is provided with a pneumatic actuator which is operable to move the bucket valve from the curl to neutral position. A pneumatic circuit includes a source of air pressure and three serially connected valves, one of which is manually operated to condition the system for automatic operation. A second valve is cam operated to open position by movement of the boom control valve to the detented float position. The third valve is cam operated to open position by retraction of the bucket cylinder beyond a predetermined point. Upon opening the manual valve and raising and dumping the bucket, movement of the boom valve to the float position automatically effects movement of the bucket control valve from neutral to the curl position so the bucket is automatically curled as the boom is lowered by gravity. After the bucket cylinder has been extended beyond the predetermined point, that valve closes, deactuating the actuator to enable return of the bucket control valve to neutral position. The parallelogram linkage upon further lowering automatically positions the bucket in a digging position. Thus only one valve need be manually operated to automatically position the bucket from a raised and dumped position into a digging position at ground level. The system further includes a second pneumatic motor for closing the boom control valve when the boom is raised to a predetermined height, as controlled by another pneumatic valve.

United States Patent Askins 1 Feb. 15,1972

[54] EARTHWORKING VEHICLE William J. Askins,Brecksville, Ohio [73] Assignee: Massey-Ferguson lnc., Detroit, Mich.

[22] Filed: Aug. 19, 1970 [21] Appl. No.: 65,072

[72] Inventor:

[52] US. Cl ..2l4/764 Primary Examiner-Gerald M. Forlenza Assistant Examiner-John Mannix Att0meyGerhardt, Greenlee & Farris [57] ABSTRACT A shovel loader having a boom, a bucket pivoted thereto, and a quadrilateral linkage interconnecting the bucket and the loader has apparatus for automatically positioning the bucket in the desired digging position. The bucket control valve is provided with a pneumatic actuator which is operable to move the bucket valve from the curl to neutral position. A pneumatic circuit includes a source of air pressure and three serially connected valves, one of which is manually operated to condition the system for automatic operation. A second valve is cam operated to open position by movement of the boom control valve to the detented float position. The third valve is cam operated to open position by retraction of the bucket cylinder beyond a predetermined point. Upon opening the manual valve and raising and dumping the bucket, movement of the boom valve to the float position automatically effects movement of the bucket control valve from neutral to the curl position so the bucket is automatically curled as the boom is lowered by gravity. After the bucket cylinder has been extended beyond the predetermined point, that valve closes, deactuating the actuator to enable return of the bucket control valve to neutral position. The parallelogram linkage upon further lowering automatically positions the bucket in a digging position. Thus only one valve need be manually operated to automatically position the bucket from a raised and dumped position into a digging position at ground level. The system further includes a second pneumatic motor for closing the boom control valve when the boom is raised to a predetermined height, as controlled by another pneumatic valve.

9 Claims, 5 Drawing Figures PATENTEDFEBISIQTZ sum in! 3 INVENTOR- W/ZZ/AM J ASK/N5 BY o WM 1% M Zi /m/Ha .PATENTEDFEB 15 I972 SHEET 2 OF 3 INVENTOR.

PATENTEDFEB 15 I972 110 NV T @E T0 ATMOS. EE- MAN. AT SJ NV I CAM ATMOS.

: PRESSURE SOURCE INVENTOR.

ATTORNEYS.

EARTIIWORKING VEHICLE This invention relates generally to earthworking vehicles and more particularly to a return-to-dig mechanism for a shovel loader.

Many implement or bucket positioning systems have been devised to facilitate the operation of a shovel loader. Such systems normally take the form of an electric, hydraulic, pneumatic or mechanical means for automatically shifting the bucket control valve from a curl position to a neutral position so that the bucket is automatically positioned in a digging position on lowering of the boom. Some systems also include means for limiting boom raisingto a predetermined height. However, the operation of such devices, although greatly simplifying operation of a loader in a cycling operation, requires the operation of both the boom valve lever to lower the boom and the bucket valve lever to curl the bucket after the bucket has been raised and dumped.

Since the shovel loader operator must also maneuver the loader while operating both the boom and bucket valve levers, fast loader cycling requires concentration and expertise. It would therefore be desirable to devise a system which could simplify the boom lowering and bucket positioning and the boom raising operations to reduce the number of manual operations necessary during loader cycling.

It is therefore an object of this invention to provide a returnto-dig mechanism for a shovel loader which requires operation of only one valve to both lower the boom and curl the bucket to an automatically predetermined digging position at ground level.

It is a further object of this invention to additionally provide a device for automatically limiting raising of the boom to a predetermined height to further facilitate operation of the loader by the operator.

In accomplishing these objects this invention provides an earth-working vehicle consisting of a boom pivoted on the vehicle, first motor means mounted on the vehicle for pivoting the boom, a first operator for controlling operation of the first motor means and movable between inoperative and operative positions to cause the motor to pivot the boom, an implement pivoted on the boom, second motor means connected to the vehicle to pivot the implement and having a range of movement including an intermediate point, a second operator for controlling operation of the second motor means, biasing means normally locating the second operator in the inoperative position, implement position control means including a power device for moving the second operator from inoperative to operative position, and a control circuit for the power device including a power source, and first and second control devices actuatable concurrently to connect the power source to the power device to effect movement of the second operator to operative position to actuate the second motor means, the first control device being actuated in response to movement of the first operator to operative position and the second control device being actuated in response to movement of the second motor means to one side of the intermediate point, the second control device being deactuated in response to movement of the second motor means to the other side of the intermediate point to enable the biasing means to locate the second operator in the inoperative position to deactuate the second motor means.

The invention further consists of a third control device manually actuatable to enable concurrent actuation of the first and second control devices to effect movement of the second operator to operative position and manually deactuatable to prevent movement of the second operator to operative position.

The invention still further consists of a second power device for moving the first operator from operative to inoperative positions, a third control device in the control circuit connecting the source with the second power device, and actuatable upon pivotal movement of the boom beyond a predetermined point relative to the vehicle to connect the source with the second power device and move the first operator to inoperative position.

Thus, this invention provides what may be termed a singlelever return-to-dig bucket positioning mechanism and further includes a boom height limiting means.

These and further objects and features of this invention will become more readily apparent upon reference to the following detailed description of the attached drawings, wherein:

FIG. 1 is a right side elevation of a shovel loader incorporating an implement position control means according to this invention and showing the bucket in a solid line lowered digging position and a phantom line curled carry position.

FIG. 2 is similar to FIG. 1 showing the bucket in a solid line raised curled position and a phantom line dumped position;

FIG. 3 is an enlarged detail view of a portion of FIG. 1;

FIG. 4 is an enlarged partial view looking in a direction indicated by lines 4-4 of FIG. 3; and 1 FIG. 5 is a schematic diagram of the control circuit for the implement position control means according to this invention. 7 An earthworking vehicle in the form of an articulated shovel loader 10 is provided with a boom structure 12 which is pivoted at 14 to the loader front section 16. Motor means in the form of a pair of double-acting hydraulic boom position control cylinders 18, only one of which is shown, are pivoted at 20 to the front section 16 and at 22 to the boom 12. The cylinders 18 are operable to lift and lower the boom 12 as shown in FIGS. 1 and 2.

An earthworking implement or bucket 24 has a flange 26 that is pivoted at 28 to the front end of the boom 12. Quadrilateral linkages 30, only one of which is shown, are provided to interconnect the bucket 24 with the front section 16 and each includes an upper link 32 which is pivoted at 34 to an upper portion of bucket support flange 26. A cross link 38 is intermediately pivoted at 40 to the boom 12 and is connected to the rearward end of upper link 32 at 42. A double-acting hydraulic bucket position control cylinder 44 is pivoted at 46 to the lower end oflink 38 and is pivoted at 48 to the front section 16.

In the solid line digging position shown in FIG. 1, the bucket cutting edge 49 lies parallel with the ground. After the bucket is filled, the cylinder 44 is extensible to rock link 38 counterclockwise and curl the bucket back to the phantom line carry position illustrated. The boom cylinder 18 can then be actuated to pivot the boom 12 counterclockwise and raise the bucket to the solid line position shown in FIG. 2. Thereupon cylinder 44 is retracted to pivot link 38 clockwise and move the bucket to the dumped position shown in phantom lines in FIG. 2.

Referring now to FIGS. 3 and 4, the controls for operating the cylinders 44 and 18 will now be described. An operators platform 50 is mounted on the rear section of loader l0 and includes an operators seat 52 and a steering wheel 54. Behind the operator's seat 52 is a valve casing 56 which includes a spring-centered boom position control valve 58 and a spring centered bucket position control valve 60. The valve 58 is connected by a linkage 62 to an operators control lever 64 that is pivoted at 66 to a control lever support 68. The linkage 62 includes a link 70, a bellcrank 72 pivoted to a body bracket at 74, and an adjustable link 76 which is pivotally connected at 78 to lever 64. Similarly, valve 60 is connected by a linkage 79 to an operator's control lever 80 that is pivoted at 66 to the support 68. The linkage for valve 60 includes a link 82, a bellcrank 84 and a link 86 pivoted to the lever 80.

Referring now to FIGS. 4 and S, the cylinders 44 are connected via conduits 90 and 92 to the valve 60 which is connected by a conduit 94 to a pump 96 and by an exhaust line 98 to a hydraulic fluid sump 100. As shown in FIG. 4, the control lever 80 is movable between a spring centered neutral position N and extreme curl and dump positions, respectively ,C and D. It is readily apparent that this movement of control lever 80 will cause reciprocation of valve 60 and will effect alternate pressurization of conduits 90 or 92 to curl and dump the bucket as shown in FIGS. 1 and 2.

In a somewhat similar manner the boom control lever 64 is movable between a spring-centered neutral position N, a detented raised position R, a power lower position L, and a detented float position F. In the raised and lowered positions, the lines 102 and 104 which connect cylinder 18 to valve 58 are alternately pressurized to raise and lower the boom as shown in FIGS. 1 and 2, while in the float position, the lines 102 and 104 are interconnected so that the fluid in these lines is freely interchangeable to permit movement of the boom by external forces, such as by gravity.

The implement position control means, as shown schematically in FIG. 5, will now be explained. The bucket control valve 60 is provided with a pneumatic fluid power device motor 106 which is operable to move the bucket control valve 60 from the spring-centered neutral position to the curl position. Device 106 is connected by a conduit 108 through control devices or valves 110, 112, 114, to a supply line 116 emanating from an air pressure source 118 which may be in the form of a compressor driven from the loader engine (not shown). Each of the valves 110, 112, 114 is a two position valve having an open position permitting the flow of air from the source 118 to the device 106 and a closed position in which the pressure in line 108 is vented to atmosphere.

The valve 110 is mounted on the cylinder 44 and has a cam follower 120 that is actuated by a rod 122 which extends through a guide 124 on the cylinder 44 and is attached at 126 to the wrist pin 128 at pivot 46. Thus valve 110 is operated in response to the extension contraction of the piston rod of cylinder 44. In the position shown in FIG. 3, the valve 110 is in closed position. As cylinder 44 is retracted, rod 122 causes a cammed opening of valve 110.

The valve 112 is mounted adjacent the vehicle steering wheel 54 as shown in FIG. 3. It is manually movable from a normally closed position as shown in FIG. to a detented open position to permit communication through conduit 108.

As best seen in FIG. 4, the valve 114 is mounted adjacent the linkage 62 immediately behind the operators seat 52. The valve 114 includes a rockable cam follower 130 which is operated by a U-shaped camming member 132 attached to link 76 of the boom valve control linkage 62. In the position shown in FIG. 4, the boom control lever 64 is in the neutral position and valve 114 is in the closed position venting to atmosphere as shown in FIG. 5. Valve 114 is not actuated by movement of lever 64 to any of the neutral, raised or lower positions. However, upon movement .of lever 64 to the detented float position, the camming member 132 will rock cam follower 130 and open valve 114 to permit communication from lines 116 to 108.

When automatic positioning of bucket 24 in the solid line digging position of FIG. 1 is desired upon movement from the phantom line FIG. 2 position, the operator first actuates valve 112 to the open position where it is held by a detent. In the FIG. 2 phantom line dump position of the bucket, cylinder 44 is retracted and valve 110 is in the open position caused by retraction of rod 122 to trip follower 120. Thus valves 110 and 112 are open while communication from source 118 to the device 106 is prevented by the closed position of valve 114.

When the operator moves lever 64 to the float position, link 76 moves rearward and trips valve 114 by contact of camming member 132 with follower 130, thereby opening valve 114 and permitting pressurization of device 106 by source 118 through lines 116 and 108 causing a shifting of the bucket control valve 60 from the neutral position to the curl position and actuating cylinders 44. Thus, as the boom 12 is lowered by gravity, the bucket 24 is curled from the fully dumped position by extension of cylinder 44. However, when cylinder 44 has extended to the position shown in FIG. 3, rod 122 disengages cam follower 120, thus closing valve 110 which depressurizes device 106, enabling spring centered movement of the bucket valve 60 to the neutral position. Regardless of the position of the boom when this operation occurs, the parallelogram linkage 30 will move the bucket 24 automatically to the solid line digging position shown in FIG. 1.

It is thus readily seen that the control system as described herein above enables automatic positioning of the bucket in the digging position upon lowering of the boom by operation of only the boom valve control lever 64. This frees the operator from having to actuate both levers and he can then concentrate on maneuvering the vehicle.

As a further feature of this invention, a boom height limiting control device is included. As shown in FIG. 5, the pneumatic circuit also includes a pneumatically operated power device 134 which is connected by a conduit 136 through a valve 138 on a line 140 and line 116 to the air pressure source 118. Actuation of device 134 causes movement of the boom control valve 58 from the detented raised position to the neutral position. The valve 138, shown best in FIG. 3, is mounted for rotation with the boom 12 and includes a pivotable cam follower 142. A camming member 144 is secured to the nonrotatable pivot 14 which is mounted to the front section 16 of the loader 10. In the position illustrated in FIG. 3, valve 138 is in the closed position shown in FIG. 5 wherein communication between source 118 and device 134 is blocked by valve 138 which vents device 134 to atmosphere.

To elevate the boom from the FIG. 1 to the FIG. 2 position, the operator moves the boom control lever 64 to the raise position where it is maintained by detent. As the boom 12 moves to a predetermined position which is controlled by the positioning of adjustable cam member 144 relative to cam follower 142, valve 138 will open, causing pressurization of device 134 which shifts the boom lever from the detented raised position to the neutral position. This action automatically limits the height of boom 12, freeing the opertors attention for loader maneuvering. To change the maximum boom height, the operator merely adjusts to rotative position of cam member 144.

The implement position control means according to this invention enables automatic positioning of the bucket in the digging position upon movement from an elevated dumped position by manipulation of only the boom control valve lever. Further this invention also provides a device for automatically limiting the boom raising to a selected predetermined height. This invention therefore enables a greatly simplified operation of the loader and enables the operator to concentrate on maneuvering the vehicle.

Although only one form of the invention has been specifically shown and described, variations thereof are contemplated within the scope of the following claims. For instance, the pneumatic system shown in the specific embodiment could readily be replaced'by an electric, hydraulic or mechanical system. This invention would further be readily usable with a loader not having a quadrilateral linkage although it is preferably designed therefor.

I claim:

1. An earthworking vehicle having a boom pivoted on the vehicle, first motor means mounted on the vehicle for pivoting the boom, a first operator for controlling operation of the first motor means and movable between inoperative and operative positions to cause the motor to pivot the boom, an implement pivoted on the boom, second motor means connected to the vehicle to pivot the implement and having a range of movement including an intermediate point, and a second operator for controlling operation of the second motor means, movable between an inoperative position and an operative position actuating the second motor means, and biasing means normally locating the second operator in the inoperative position, characterized by implement position control means including a power device for moving the second operator from inoperative to operative position, and a control circuit for the power device including a power source, and first and second control devices actuatable concurrently to connect the power source to the power device to effect movement of the second operator to operative position to actuate the second motor means, the first control device being actuated in response to movement of the first operator to operative position and the second control device being actuated in response to movement of the second motor means to one side of the intermediate point, the second control device being deactuated in response to movement of the second motor means to the other side of the intermediate point to enable the biasing means to locate the second operator in the inoperative position to deactuate the second motor means.

2. An earthworking vehicle according to claim 1, wherein the control circuit includes a third control device manually actuatable to enable the concurrent actuation of the first and second control devices to effect movement of the second operator to operative position and manually deactuatable to prevent movement of the second operator to operative position.

3. An earthworking vehicle according to claim 1, wherein the power device is a fluid powered device, the control circuit is a pressure fluid circuit, the power source is a power fluid source, and the first and second control means are valves in the circuit.

4. An earthworking vehicle according to claim 3, wherein the control circuit includes a manually operable third valve having an open position permitting communication between the source and the fluid powered device as controlled by the first and second valves and a closed position preventing communication between the source and the fluid powered device.

5. An earthworking vehicle according to claim 1, wherein the implement position control means include a second power device for moving the first operator from operative to inoperative positions, a third control device in the control circuit connecting the source with the second power device, and actuatable upon pivotal movement of the boom beyond a predetermined point relative to the vehicle to connect the source with the second power device and move the first operator to inoperative position.

6. An earthworking vehicle having a boom pivoted on the vehicle for movement between raised and lowered positions; a first double-acting hydraulic motor mounted on the vehicle for pivoting the boom; a hydraulic power fluid source on the vehicle; a first control circuit including a first valve interconnecting the source and the first motor, the first valve being movable between a neutral position immobilizing the first motor, alternative raise and lower positions enabling power operation of the first motor and a detented float position enabling fluid circulation within the motor; an earthworking bucket pivotally mounted on the boom for movement between curled and dumped positions; a quadrilateral linkage interconnecting the bucket and the vehicle for automatically pivoting the bucket on the boom upon boom movement, said linkage including a second double-acting hydraulic motor extensible and retractable to curl and dump the bucket; the first circuit including a second valve interconnecting the source and the second motor, the second valve being movable between a neutral position immobilizing the second motor and altemative curl and dump positions enabling power operation of the second motor; and biasing means biasing the second valve to neutral position, characterized by bucket position control means including a fluid power device for moving the second valve to curl position; a second power fluid source; a second control circuit connecting the second source to the device including third and fourth valves in series, the third and fourth valves being concurrently openable to actuate the device; a third valve actuator responsive to movement of the first valve to lower position to open the third valve; and a fourth valve actuator responsive to retraction of the second motor beyond a predetermined point to open the fourth valve to enable actuation of the device to move the second valve to curl position, and responsive to contraction of the second motor beyond the predetermined point to close the fourth valve to deactuate the device and enable the biasing means to move the second valve to neutral position to deactuate the second motor.

7. An earthworking vehicle according to claim 6, wherein the second circuit includes a fifth valve in series with the third and fourth valves, manually openable to enable the concurrent opening of the first and second valves to actuate the fluid power device and manually closable todeactuate the device.-

. An earthworking vehicle according to claim 7, wherein the bucket position control means include a second fluid power device for moving the first valve from raise to neutral position, a sixth valve in the second circuit connecting the second source to the second device, and a sixth valve actuator openable in response to raising movement of the boom to a predetermined height to interconnect the second source and the second device to move the first valve from raise to neutral position.

9. An earthworking vehicle having a boom pivoted on the vehicle, first motor means mounted on the vehicle for pivoting the boom, a first operator for controlling operation of the first motor means and movable between inoperative and operative positions to cause the motor to pivot the boom, an implement pivoted on the boom, second motor means connected to the vehicle to pivot the implement and having a range of movement including an intermediate point, and a second operator for controlling operation of the second motor means, movable between an inoperative position and an operative position actuating the second motor means, and biasing means normally locating the second operator in the inoperative position, characterized by implement position control means including actuating means for moving the second operator from inoperative to operative position in response to movement of the first operator to operative position when the second motor means is positioned to one side of the intermediate point and position responsive means responsive to movement of the second motor means to the other side of the intermediate point to deactuate the actuating means and effect movement of the second operator from operative to inoperative position. 

1. An earthworking vehicle having a boom pivoted on the vehicle, first motor means mounted on the vehicle for pivoting the boom, a first operator for controlling operation of the first motor means and movable between inoperative and operative positions to cause the motor to pivot the boom, an implement pivoted on the boom, second motor means connected to the vehicle to pivot the implement and having a range of movement including an intermediate point, and a second operator for controlling operation of the second motor means, movable between an inoperative position and an operative position actuating the second motor means, and biasing means normally locating the second operator in the inoperative position, characterized by implement position control means including a power device for moving the second operator from inoperative to operative position, and a control circuit for the power device including a power source, and first and second control devices actuatable concurrently to connect the power source to the power device to effect movement of the second operator to operative position to actuate the second motor means, the first control device being actuated in response to movement of the first operator to operative position and the second control device being actuated in response to movement of the second motor means to one side of the intermediate point, the second control device being deactuated in response to movement of the second motor means to the other side of the intermediate point to enable the biasing means to locate the second operator in the inoperative position to deactuate the second motor means.
 2. An earthworking vehicle according to claim 1, wherein the control circuit includes a third control device manually actuatable to enable the concurrent actuation of the first and second control devices to effect movement of the second operator to operative position and manually deactuatable to prevent movement of the second operator to operative position.
 3. An earthworking vehicle according to claim 1, wherein the power device is a fluid powered device, the control circuit is a pressure fluid circuit, the power source is a power fluid source, and the first and second control means are valves in the circuit.
 4. An earthworking vehicle according to claim 3, wherein the control circuit includes a manually operable third valve having an open position permitting communication between the source and the fluid powered device as controllEd by the first and second valves and a closed position preventing communication between the source and the fluid powered device.
 5. An earthworking vehicle according to claim 1, wherein the implement position control means include a second power device for moving the first operator from operative to inoperative positions, a third control device in the control circuit connecting the source with the second power device, and actuatable upon pivotal movement of the boom beyond a predetermined point relative to the vehicle to connect the source with the second power device and move the first operator to inoperative position.
 6. An earthworking vehicle having a boom pivoted on the vehicle for movement between raised and lowered positions; a first double-acting hydraulic motor mounted on the vehicle for pivoting the boom; a hydraulic power fluid source on the vehicle; a first control circuit including a first valve interconnecting the source and the first motor, the first valve being movable between a neutral position immobilizing the first motor, alternative raise and lower positions enabling power operation of the first motor and a detented float position enabling fluid circulation within the motor; an earthworking bucket pivotally mounted on the boom for movement between curled and dumped positions; a quadrilateral linkage interconnecting the bucket and the vehicle for automatically pivoting the bucket on the boom upon boom movement, said linkage including a second double-acting hydraulic motor extensible and retractable to curl and dump the bucket; the first circuit including a second valve interconnecting the source and the second motor, the second valve being movable between a neutral position immobilizing the second motor and alternative curl and dump positions enabling power operation of the second motor; and biasing means biasing the second valve to neutral position, characterized by bucket position control means including a fluid power device for moving the second valve to curl position; a second power fluid source; a second control circuit connecting the second source to the device including third and fourth valves in series, the third and fourth valves being concurrently openable to actuate the device; a third valve actuator responsive to movement of the first valve to lower position to open the third valve; and a fourth valve actuator responsive to retraction of the second motor beyond a predetermined point to open the fourth valve to enable actuation of the device to move the second valve to curl position, and responsive to contraction of the second motor beyond the predetermined point to close the fourth valve to deactuate the device and enable the biasing means to move the second valve to neutral position to deactuate the second motor.
 7. An earthworking vehicle according to claim 6, wherein the second circuit includes a fifth valve in series with the third and fourth valves, manually openable to enable the concurrent opening of the first and second valves to actuate the fluid power device and manually closable to deactuate the device.
 8. An earthworking vehicle according to claim 7, wherein the bucket position control means include a second fluid power device for moving the first valve from raise to neutral position, a sixth valve in the second circuit connecting the second source to the second device, and a sixth valve actuator openable in response to raising movement of the boom to a predetermined height to interconnect the second source and the second device to move the first valve from raise to neutral position.
 9. An earthworking vehicle having a boom pivoted on the vehicle, first motor means mounted on the vehicle for pivoting the boom, a first operator for controlling operation of the first motor means and movable between inoperative and operative positions to cause the motor to pivot the boom, an implement pivoted on the boom, second motor means connected to the vehicle to pivot the implement and having a range of movement including an intermediate point, and a second operator for controlling operation of the second motor means, movable between an inoperative position and an operative position actuating the second motor means, and biasing means normally locating the second operator in the inoperative position, characterized by implement position control means including actuating means for moving the second operator from inoperative to operative position in response to movement of the first operator to operative position when the second motor means is positioned to one side of the intermediate point and position responsive means responsive to movement of the second motor means to the other side of the intermediate point to deactuate the actuating means and effect movement of the second operator from operative to inoperative position. 